The present invention relates to self-cleaning ovens and in particular, to a system for controlling the operation of a self-cleaning oven.
During the use of an oven of an electric or gas range, deposits will generally accumulate as a result of spills, boil overs and other unintended release of foods from their cooking containers. In order to ease the cleaning of the spillage, provision is made in some ranges, known as xe2x80x9cself-cleaningxe2x80x9d ranges, to raise the temperature of the cooking cavity well above that which would be used in cooking in order to carbonize or bum out the residue. In general, this is achieved by the selection through the range""s controls of a self-clean cycle. Initiation of this cycle typically sets a high control temperature for the range, locks the oven door at some predetermined time or temperature and proceeds to heat the cavity to a relatively high temperature for a predetermined time before ending the cycle, allowing cooling to occur and then releasing the door lock as an end to the cycle.
Typically, the time period set for this self-clean cycle is determined by the assumption of a worst case cycle. During the cycle, odors or even smoke may be released in the range environment and significant energy is used to hold the cooking cavity at a high temperature. Because of odor and smoke release, users are advised to open windows and will frequently leave the kitchen area for an extended period of time while self-clean is performed.
If a method can be devised which adjusts the time of self-cleaning to that needed for the existing degree of soil accumulation, then cycle times and their negative impact on kitchen environment and energy usage can be minimized.
U.S. Pat. No. 4,954,694 discloses a self-cleaning oven which incorporates a heat controlled unit which is responsive to a gas signal from a gas sensor located in the exhaust passage. The gas sensor measures humidity or carbon dioxide levels. The heat control samples the gas signal at a given time interval to detect a variation of amount of the gas component and detect a first inflection point from decreasing to increasing or visa versa in a gas-component variation and a second inflection point from decreasing to increasing or vice versa in the gas component variation after detection of the first inflection point. The heat control means determines the heating time period for cleaning in correspondence with the second inflection point. An oxidizing catalyst is provided in the exhaust passage, upstream of the gas sensor.
It is generally recognized that the combustion of food product will generate various gases or gas components. This invention is generally directed to controlling the operation of a self cleaning oven wherein the duration of a self clean cycle is responsive to the amount of soil accumulation in the oven.
According to the present invention, the duration of the self-clean cycle is determined by monitoring the usage of the oven and the frequency of the self cleaning cycle. The amount of clean time needed to perform the self-cleaning cycle is determined by monitoring the number or length of bake and broil cycles the user has performed since the last self-clean cycle is counted. The number of days since a self-clean cycle has been run is also counted. A minimum clean base time based on these factors is then be determined. Thus, when the user selects and starts a clean cycle, the number or length of bake and broil cycles and the number of days the oven has not been cleaned, are retrieved and used to determine the appropriate clean time. The calculated clean time is displayed to the user to show the length of the clean cycle.